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Clinical anatomy ‘Thorax’
(Snell & KLM)
Dr M Idris Siddiqui
CERVICAL RIB
A cervical rib occurs in approximately 0.5% of persons.
It arises from the transverse process of the seventh
...
CERVICAL
RIB
Role of Costal Cartilages
Costal cartilages prolong the ribs
anteriorly and contribute to the
elasticity of the thoracic w...
Rib Fractures
The weakest part of a rib is just anterior to
its angle. Rib fractures commonly result
from direct blows or ...
Flail Chest
Flail chest occurs when a sizable segment of the
anterior and/or lateral thoracic wall moves freely
because of...
Supernumerary Ribs
People usually have 12 ribs on each side, but the number
may be increased by the presence of cervical a...
Sternal Fractures
Sternal fractures are not common, but crush injuries
can occur during traumatic compression of the
thora...
Median Sternotomy
To gain access to the thoracic cavity for
surgical procedures—on the heart and
great vessels, for exampl...
Sternal Biopsies
The sternal body is often used for bone marrow
needle biopsy because of its breadth and
subcutaneous posi...
Paralysis of Diaphragm
One can detect paralysis of the diaphragm
radiographically by noting its paradoxical
movement. Para...
Thoracotomy, Intercostal Space Incisions
The surgical creation of an opening through the thoracic wall
to enter a pleural ...
Rib Excision
• Surgeons use an H-shaped incision to incise the
superficial aspect of the periosteum that ensheaths
the rib...
THORACIC OUTLET SYNDROMES
The brachial plexus of nerves (C5, 6, 7,
8, and T1) and the subclavian artery
and vein are close...
Thoracic Out let Syndrome
When clinicians refer to the superior thoracic
aperture as the thoracic “outlet,” they are
empha...
Dislocation of Ribs
A rib dislocation ( slipping rib syndrome) or dislocation
of a sternocostal joint is the displacement ...
STERNAL ANGLE AS AN IMPORTANT
CLINICAL BONY LANDMARK
The position of the sternal angle that is, the
angle between the manu...
NEEDLE THORACOSTOMY
A needle thoracostomy is necessary for
patients with tension pneumothorax or
with a large hemothorax.
...
PENETRATING INJURIES OF THE
DIAPHRAGM
Any penetrating wound to the chest below
the level of the nipples should be
suspecte...
SKIN INNERVATION OF
THE CHESTWALL AND DISEASE
Above the level of the sternal angle, the nerve supply to the skin of the
an...
Breast Quadrants
For the anatomical location and
description of pathology (e.g., cysts
and tumors), the breast is divided
...
Changes in Breasts
Changes, such as branching of the lactiferous ducts, occur
in the breast tissues during the menstrual c...
Carcinoma of Breast
Understanding the lymphatic drainage of the breasts is of practical importance in predicting the
metas...
Carcinoma of Breast
• Because most of the lymphatic drainage of the breast is to the axillary
lymph nodes, they are the mo...
Mammography
Radiographic examination of the breasts,
mammography, is one of the techniques used to
detect breast masses.
A...
Surgical Incisions of Breast
Incisions are placed in the inferior breast quadrants when
possible because these quadrants a...
Mastectomy
Mastectomy (breast excision) is not as common as it once
was as a treatment for breast cancer.
In simple mastec...
Herpes Zoster Infection
• Herpes zoster ( shingles)—a viral disease of
spinal ganglia—is a dermatomally
distributed skin l...
Dyspnea—Difficult Breathing
When people with respiratory problems such
as asthma or emphysema or with heart
failure strugg...
Intercostal Nerve Block
Local anesthesia of an intercostal space is produced by
injecting a local anesthetic agent around ...
CORONARY HEART DISEASE AND
THE INTERCOSTOBRACHIAL NERVE
In coronary heart disease pain is
often referred along the
interco...
DEFLECTION OF THEMEDIASTINUM
In the living, the mediastinum is very mobile. If
air should enter the pleural cavity as the
...
INHALED FOREIGN BODIES
• Because the right bronchus is wider
and more direct continuation of the
trachea, foreign bodies t...
PNEUMOTHORAX
• As the result of disease or injury,
air can enter the pleural cavity
from the lungs or through the
chest wa...
PAIN AND LUNG DISEASE
Lung tissue and the visceral pleura are
insensitive to pain (supplied by autonomic
nerves and devoid...
HEART SOUNDS
The heart makes two sounds: lu¯b, and du˘ p. The first
sound is produced by the contraction of the ventricles...
FAILURE OF THE CONDUCTING
SYSTEM OF THE HEART
The atrioventricular bundle is the only route by
which the cardiac impulse c...
CORONARY ARTERY DISEASE
Although the coronary arteries have numerous
anastomoses at the arteriolar level, they are
essenti...
CARDIAC PAIN
Pain originating in the heart as the result of ischemia results in
the stimulation of the sensory nerve endin...
Atrial Septal Defect
In 25% of individuals, the foramen ovale
does not completely close. When the
opening is small, it has...
Ventricular Septal Defects
The ventricular septum is normally formed by
fusion of the small, membranous upper part
with th...
Tetralogy of Fallot
The following four defects occur with tetralogy of
Fallot
• Large ventricular septal defeat.
• Stenosi...
Patent Ductus Arteriosus
Normally, the ductus arteriosus has closed
by the end of the first month after birth.
Failure of ...
Coarctation of the Aorta
Coarctation of the aorta is a narrowing of the aorta
just proximal, opposite, or distal to the si...
AZYGOS VEINS AND CAVAL
OBSTRUCTION
In obstruction of the superior or
inferior venae cavae, the azygos
veins provide an alt...
LOWER THIRD OF ESOPHAGUS AS SITE OF
PORTOSYSTEMIC ANASTOMOSIS
At the lower third of the esophagus, the tributaries of
the ...
Surface Anatomy of Thoracic Wall
Several bony landmarks and imaginary lines facilitate anatomical descriptions,
identifica...
Additional lines (not illustrated) are extrapolated along borders of bony
formations—for example,
the parasternal line (G....
Surface Anatomy of Thoracic Wall
The sternal angle is a palpable landmark that lies at the level of the second pair of cos...
Pulmonary Collapse
If a sufficient amount of air enters the pleural cavity,
the surface tension adhering visceral to parie...
Pneumothorax, Hydrothorax,
Hemothorax, and Chylothorax
Entry of air into the pleural cavity—pneumothorax —resulting from a...
Pleuritis
During inspiration and expiration, the normally moist,
smooth pleurae make no sound detectable by
auscultation (...
Variation in Lobes of Lungs
• Occasionally, an extra fissure divides a lung or a
fissure is absent. For example, the left ...
Thoracentesis
• Sometimes it is necessary to insert a
hypodermic needle through an
intercostal space into the pleural cavi...
Auscultation and Percussion of Lungs
Auscultation of the lungs (assessing air flow through the
tracheobronchial tree into ...
Aspiration of Foreign Bodies
Because the right bronchus is wider and shorter
and runs more vertically than the left ronchu...
Lung Resections
Knowledge of the anatomy of the bronchopulmonary segments
is essential for precise interpretations of diag...
Injury to Pleurae
The visceral pleura is insensitive to pain because its innervation
is autonomic (motor and visceral affe...
Thoracoscopy
Thoracoscopy is a diagnostic and sometimes
therapeutic procedure in which the pleural
cavity is examined with...
Pulmonary Embolism
Obstruction of a pulmonary artery by a blood clot (embolus) is a
common cause of morbidity (sickness) a...
Inhalation of Carbon Particles
• Lymph from the lungs carries phagocytes,
cells possessing the property of ingesting
carbo...
Bronchogenic Carcinoma
Bronchogenic carcinoma is a common type of lung cancer
that arises from the epithelium of the bronc...
Bronchoscopy
When examining the bronchi with a bronchoscope —
an endoscope for inspecting the interior of the
tracheobronc...
Surgical Significance of Transverse
Pericardial Sinus
The transverse pericardial sinus is especially important to
cardiac ...
Pericarditis and Pericardial Effusion
Inflammation of the pericardium (pericarditis) usually
causes chest pain. Normally, ...
Cardiac Tamponade
Cardiac tamponade (heart compression) is a potentially lethal
condition because the fibrous pericardium ...
Levels of Viscera in Mediastinum
The level of the viscera relative to the mediastinal
subdivisions depends on the position...
Percussion of Heart
Percussion defines the density and size of the heart. The
classic percussion technique is to create vi...
Atrial and Ventricular Septal Defects
Congenital anomalies of the interatrial septum —usually related to incomplete
closur...
Thrombi
Thrombi (clots) form on the walls of the left atrium in
certain types of heart disease. If these thrombi
detach or...
Valvular Heart Disease
Disorders involving the valves of the heart disturb the pumping efficiency of
the heart. Valvular h...
valvuloplasty
Because valvular diseases are mechanical problems,
damaged or defective cardiac valves are often
replaced su...
Valve stenosis
A prolapsed mitral valve is an insufficient or incompetent valve
in which one or both leaflets are enlarged...
Coronary Artery Disease or Coronary
Heart Disease
Coronary artery disease (CAD) is one of
the leading causes of death. It ...
Myocardial Infarction
With sudden occlusion of a major artery by an embolus
(G. embolos, plug), the region of myocardium s...
Coronary Atherosclerosis
The atherosclerot ic process, characterized by
lipid deposits in the intima (lining layer) of
the...
Coronary Bypass Graft
Patients with obstruction of their coronary circulation and severe angina
may undergo a coronary byp...
Coronary Angioplasty
In selected patients, surgeons use percutaneous transluminal
coronary angioplasty, in which they pass...
Variations of Coronary Arteries
Variations in the branching patterns of the coronary arteries are
common. In the most comm...
Echocardiography
Echocardiography (ultrasonic cardiography) is a method of
graphically recording the position and motion o...
Cardiac Referred Pain
The heart is insensitive to touch, cutting, cold, and heat; however, ischemia
and the accumulation o...
Injury to Conducting System of Heart
Damage to the conducting system, often resulting from
ischemia caused by coronary art...
Laceration of Thoracic Duct
• Because the thoracic duct is thin-walled and
may be colorless, it may not be easily
identifi...
Collateral Venous Routes to Heart
The azygos, hemiazygos, and accessory hemiazygos veins offer
alternate means of venous d...
Aneurysm of Ascending Aorta
The distal part of the ascending aorta receives a strong
thrust of blood when the left ventric...
Injury to Recurrent Laryngeal Nerves
The recurrent laryngeal nerves supply all the intrinsic
muscles of the larynx, except...
Variat ions of Great Arteries
The most superior part of the arch of the aorta is usually
approximately 2.5 cm inferior to ...
Coarctation of Aorta
• In coarctat ion of the aorta, the arch of the aorta
or descending aorta has an abnormal narrowing
(...
Age Changes in Thymus
The thymus is a prominent feature of the superior
mediastinum during infancy and childhood. In
some ...
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
Clinical anatomy thorax
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Clinical anatomy thorax

  1. 1. Clinical anatomy ‘Thorax’ (Snell & KLM) Dr M Idris Siddiqui
  2. 2. CERVICAL RIB A cervical rib occurs in approximately 0.5% of persons. It arises from the transverse process of the seventh cervical vertebra. It may have a free anterior end, may be connected to the first rib by a fibrous band, or may articulate with the first rib. • It also may cause pressure on the lower trunk of the brachial plexus or the subclavian artery, leading to symptoms and signs that are referred to as the thoracic outlet syndrome.
  3. 3. CERVICAL RIB
  4. 4. Role of Costal Cartilages Costal cartilages prolong the ribs anteriorly and contribute to the elasticity of the thoracic wall, preventing many blows from fracturing the sternum and/or ribs. In elderly people, the costal cartilages undergo calcification, making them radiopaque and less resilient.
  5. 5. Rib Fractures The weakest part of a rib is just anterior to its angle. Rib fractures commonly result from direct blows or indirectly from crushing injuries. The middle ribs are most commonly fractured. Direct violence may fracture a rib anywhere, and its broken ends may injure internal organs such as a lung or the spleen.
  6. 6. Flail Chest Flail chest occurs when a sizable segment of the anterior and/or lateral thoracic wall moves freely because of multiple rib fractures. This condition allows the loose segment of the wall to move paradoxically (inward on inspiration and outward on expiration). Flail chest is an extremely painful injury and impairs ventilation, thereby affecting oxygenation of the blood. During treatment, the loose segment is often fixed by hooks and/or wires so that it cannot move.
  7. 7. Supernumerary Ribs People usually have 12 ribs on each side, but the number may be increased by the presence of cervical and/or lumbar ribs or decreased by failure of the 12th pair to form. Cervical ribs (present in up to 1% of people) articulate with the C7 vertebra and are clinically significant because they may compress spinal nerves C8 and T1 or the inferior trunk of the brachial plexus supplying the upper limb. Tingling and numbness may occur along the medial border of the forearm. They may also compress the subclavian artery, resulting in ischemic muscle pain (caused by poor blood supply) in the upper limb. Lumbar ribs are less common than cervical ribs, but have clinical significance in that they may confuse the identification of vertebral levels in diagnostic images.
  8. 8. Sternal Fractures Sternal fractures are not common, but crush injuries can occur during traumatic compression of the thoracic wall (e.g., in automobile accidents when the driver's chest is driven into the steering column). When the body of the sternum is fractured, it is usually a comminuted fracture (broken into several pieces). The most common site of sternal fractures is the sternal angle, resulting in dislocation of the manubriosternal joint. In sternal injuries the concern is for the likelihood of heart and pulmonary injury.
  9. 9. Median Sternotomy To gain access to the thoracic cavity for surgical procedures—on the heart and great vessels, for example—the sternum is divided (“split”) in the median plane and retracted (spread apart). After surgery, the halves of the sternum are reunited and held together with wire sutures.
  10. 10. Sternal Biopsies The sternal body is often used for bone marrow needle biopsy because of its breadth and subcutaneous position. The needle pierces the thin cortical bone and enters the vascular trabecular (spongy) bone. Sternal biopsy is commonly used to obtain specimens of bone marrow for transplantation and for detection of metastatic cancer.
  11. 11. Paralysis of Diaphragm One can detect paralysis of the diaphragm radiographically by noting its paradoxical movement. Paralysis of half of the diaphragm because of injury to its motor supply from the phrenic nerve does not affect the other half because each dome has a separate nerve supply. Instead of descending on inspiration, the paralyzed dome is pushed superiorly by the abdominal viscera that are being compressed by the active side. The paralyzed dome descends during expiration as it is pushed down by the positive pressure in the lungs
  12. 12. Thoracotomy, Intercostal Space Incisions The surgical creation of an opening through the thoracic wall to enter a pleural cavity is called a thoracotomy. An anterior thoracotomy may involve making H-shaped cuts through the perichondrium of one or more costal cartilages and then shelling out segments of costal cartilage to gain entrance to the thoracic cavity. The posterolateral aspects of the fifth to seventh intercostal spaces are important sites for posterior thoracotomy incisions. In general, a lateral approach is most satisfactory for entry through the thoracic cage . With the patient lying on the contralateral side, the upper limb is fully abducted, placing the forearm beside the patient's head. This elevates and laterally rotates the inferior angle of scapula, allowing access as high as the fourth intercostal space.
  13. 13. Rib Excision • Surgeons use an H-shaped incision to incise the superficial aspect of the periosteum that ensheaths the rib, strip the periosteum from the rib, and then remove a wide segment of the rib to gain better access, as might be required to enter the thoracic cavity and remove a lung (pneumonectomy), for example. • In the rib's absence, entry into the thoracic cavity can be made through the deep aspect of the periosteal sheath, sparing the adjacent intercostal muscles. After the operation, the missing pieces of ribs regenerate from the intact periosteum, although imperfectly.
  14. 14. THORACIC OUTLET SYNDROMES The brachial plexus of nerves (C5, 6, 7, 8, and T1) and the subclavian artery and vein are closely related to the upper surface of the first rib and the clavicle as they enter the upper limb. It is here that the nerves or blood vessels may be compressed between the bones.
  15. 15. Thoracic Out let Syndrome When clinicians refer to the superior thoracic aperture as the thoracic “outlet,” they are emphasizing the important nerves and arteries that pass through this aperture into the lower neck and upper limb. Hence various types of thoracic outlet syndromes exist, such as the costoclavicular syndrome—pallor and coldness of the skin of the upper limb and diminished radial pulse resulting from compression of the subclavian artery between the clavicle and the first rib, particularly when the angle between the neck and the shoulder is increased.
  16. 16. Dislocation of Ribs A rib dislocation ( slipping rib syndrome) or dislocation of a sternocostal joint is the displacement of a costal cartilage from the sternum. This causes severe pain, particularly during deep respiratory movements. The injury produces a lump-like deformity at the dislocation site. Rib dislocations are common in body contact sports, and possible complications are pressure on or damage to nearby nerves, vessels, and muscles. A rib separation refers to dislocation of a costochondral junction between the rib and its costal cartilage. In separations of the third through tenth ribs, tearing of the perichondrium and periosteum usually occurs. As a result, the rib may move superiorly, overriding the rib above and causing pain.
  17. 17. STERNAL ANGLE AS AN IMPORTANT CLINICAL BONY LANDMARK The position of the sternal angle that is, the angle between the manubrium sterni and the body of the sternum can be easily felt and is often seen as a transverse ridge. It lies at the level of the second costal cartilage and second rib. All other ribs and costal cartilages can be counted from this point.
  18. 18. NEEDLE THORACOSTOMY A needle thoracostomy is necessary for patients with tension pneumothorax or with a large hemothorax. The purpose is to remove the air or blood to allow the lung to reexpand. The needle should be kept close to the upper border of the rib to avoid injuring the intercostal vessels and nerve in the subcostal groove.
  19. 19. PENETRATING INJURIES OF THE DIAPHRAGM Any penetrating wound to the chest below the level of the nipples should be suspected of causing damage to the diaphragm until proved otherwise. The arching domes of the diaphragm can reach the level of the fifth rib (the right dome can reach a higher level).
  20. 20. SKIN INNERVATION OF THE CHESTWALL AND DISEASE Above the level of the sternal angle, the nerve supply to the skin of the anterior chest wall and shoulder region is derived from the supraclavicular nerves (C3 and 4). Referred pain from the gallbladder can be felt on the point of the shoulder by way of these nerves (see p. 56). Below the level of the sternal angle, the anterior and lateral cutaneous branches of the intercostal nerves supply oblique bands of skin (dermatomes) in regular sequence. Since the seventh to the eleventh intercostal nerves also supply dermatomes on the anterior abdominal wall, muscles of the anterior abdominal wall, and parietal peritoneum, this fact becomes of great clinical importance. Disease in the thoracic wall may be revealed as pain in a dermatome that extends across the chest wall into the abdominal wall.
  21. 21. Breast Quadrants For the anatomical location and description of pathology (e.g., cysts and tumors), the breast is divided into four quadrants. The axillary tail is an extension of the mammary gland of the superolateral quadrant.
  22. 22. Changes in Breasts Changes, such as branching of the lactiferous ducts, occur in the breast tissues during the menstrual cycle and pregnancy. Although mammary glands are prepared for secretion by midpregnancy, they do not produce milk until shortly after the baby is born. Colostrum, a creamy white to yellowish premilk fluid, may secrete from the nipples during the last trimester of pregnancy and during initial episodes of nursing. Colostrum is believed to be especially rich in protein, immune agents, and a growth factor affecting the infant's intestines. In multiparous women (those who have given birth two or more times), the breasts often become large and pendulous. The breasts in elderly women are usually small because of the decrease in fat and the atrophy of glandular tissue.
  23. 23. Carcinoma of Breast Understanding the lymphatic drainage of the breasts is of practical importance in predicting the metastasis (dispersal) of cancer cells from a carcinoma of the breast (breast cancer). Carcinomas of the breast are malignant tumors, usually adenocarcinomas arising from the epithelial cells of the lactiferous ducts in the mammary gland lobules. Metastatic cancer cells that enter a lymphatic vessel usually pass through two or three groups of lymph nodes before entering the venous system. Breast cancer can spread via lymphatics and veins and as well as by direct invasion.Interference with the lymphatic drainage by cancer may cause lymphedema (edema, excess fluid in the subcutaneous tissue), which in turn may result in deviation of the nipple and a thickened, leatherlike appearance of the skin . Prominent or “puffy” skin between dimpled pores gives it an orange-peel appearance (peau d'orange sign). Larger dimples (fingertip size or bigger) result from cancerous invasion of the glandular tissue and fibrosis (fibrous degeneration), which causes shortening or places traction on the suspensory ligaments. Subareolar breast cancer may cause inversion of the nipple by a similar mechanism involving the lactiferous ducts. Breast cancer typically spreads by means of lymphatic vessels (lymphogenic metastasis), which carry cancer cells from the breast to the lymph nodes, chiefly those in the axilla. The cells lodge in the nodes, producing nests of tumor cells (metastases). Abundant communications among lymphatic pathways and among axillary, cervical, and parasternal nodes may also cause metastases from the breast to develop in the supraclavicular lymph nodes, the opposite breast, or the abdomen.
  24. 24. Carcinoma of Breast • Because most of the lymphatic drainage of the breast is to the axillary lymph nodes, they are the most common site of metastasis from a breast cancer. Enlargement of these palpable nodes suggests the possibility of breast cancer and may be key to early detection. • However, the absence of enlarged axillary lymph nodes is no guarantee that metastasis from a breast cancer has not occurred because the malignant cells may have passed to other nodes, such as the infraclavicular and supraclavicular lymph nodes. • Nodal metastatic breast cancer can be difficult to manage because of the complex system of lymphatic drainage. The posterior intercostal veins drain into the azygos/hemiazygos system of veins alongside the bodies of the vertebrae and communicate with the internal vertebral venous plexus surrounding the spinal cord. • Cancer cells can also spread from the breast by these venous routes to the vertebrae and from there to the cranium and brain. Cancer also spreads by contiguity (invasion of adjacent tissue). When breast cancer cells invade the retromammary space, attach to or invade the pectoral fascia overlying the pectoralis major, or metastasize to the interpectoral nodes, the breast elevates when the muscle contracts. This movement is a clinical sign of advanced cancer of the breast.
  25. 25. Mammography Radiographic examination of the breasts, mammography, is one of the techniques used to detect breast masses. A carcinoma appears as a large, jagged density in the mammogram. The skin is thickened over the tumor . The lower leader points to the nipple, which is depressed in the mammogram. Surgeons use mammography as a guide when removing breast tumors, cysts, and abscesses.
  26. 26. Surgical Incisions of Breast Incisions are placed in the inferior breast quadrants when possible because these quadrants are less vascular than the superior ones. The transition between the thoracic wall and breast is most abrupt inferiorly, producing a line, crease, or deep skin fold—the inferior cutaneous crease. Incisions made along this crease will be least evident and may actually be hidden by overlap of the breast. Incisions that must be made near the areola or on the breast itself are usually directed radially to either side of the nipple (Langer tension lines run transversely here) or circumferentially.
  27. 27. Mastectomy Mastectomy (breast excision) is not as common as it once was as a treatment for breast cancer. In simple mastectomy, the breast is removed down to the retromammary space. Radical mastectomy, a more extensive surgical procedure, involves removal of the breast, pectoral muscles, fat, fascia, and as many lymph nodes as possible in the axilla and pectoral region. In current practice, often only the tumor and surrounding tissues are removed—a lumpectomy or quadrantectomy (known as breast-conserving surgery, a wide local excision)— followed by radiation therapy
  28. 28. Herpes Zoster Infection • Herpes zoster ( shingles)—a viral disease of spinal ganglia—is a dermatomally distributed skin lesion. The herpes virus invades a spinal ganglion and is transported along the axon to the skin, where it produces an infection that causes a sharp burning pain in the dermatome supplied by the involved nerve. A few days later, the skin of the dermatome becomes red and vesicular eruptions appear.
  29. 29. Dyspnea—Difficult Breathing When people with respiratory problems such as asthma or emphysema or with heart failure struggle to breathe, they use their accessory respiratory muscles to assist the expansion of their thoracic cavities. They typically lean on a table or their thighs to fix their pectoral girdles (clavicles and scapulae) so the muscles are able to act on their rib attachments and expand the thorax
  30. 30. Intercostal Nerve Block Local anesthesia of an intercostal space is produced by injecting a local anesthetic agent around the intercostal nerves. This procedure, an intercostal nerve block, involves infiltration of the anesthetic around the intercostal nerve and its collateral branches. Because any particular area of skin usually receives innervation from two adjacent nerves, considerable overlapping of contiguous dermatomes occurs. Therefore, complete loss of sensation usually does not occur unless two or more intercostal nerves in adjacent intercostal spaces are anesthetized.
  31. 31. CORONARY HEART DISEASE AND THE INTERCOSTOBRACHIAL NERVE In coronary heart disease pain is often referred along the intercostobrachial nerve to the medial side of the arm.
  32. 32. DEFLECTION OF THEMEDIASTINUM In the living, the mediastinum is very mobile. If air should enter the pleural cavity as the result of chest trauma or lung disease, the lung on that side collapses and the mediastinum is displaced to the opposite side. Thus on physical examination the trachea and heart are found to be displaced to the opposite side.
  33. 33. INHALED FOREIGN BODIES • Because the right bronchus is wider and more direct continuation of the trachea, foreign bodies tend to enter the right instead of the left bronchus. • From there they usually pass into the middle or lower lobe bronchi.
  34. 34. PNEUMOTHORAX • As the result of disease or injury, air can enter the pleural cavity from the lungs or through the chest wall; this condition is known as pneumothorax
  35. 35. PAIN AND LUNG DISEASE Lung tissue and the visceral pleura are insensitive to pain (supplied by autonomic nerves and devoid of pain-sensitive nerve endings). Once lung disease crosses the pleural cavity to involve the parietal pleura, pain becomes a prominent feature (supplied by intercostal and phrenic nerves with pain- sensitive nerve endings).
  36. 36. HEART SOUNDS The heart makes two sounds: lu¯b, and du˘ p. The first sound is produced by the contraction of the ventricles and the closure of the tricuspid and the mitral valves. The second, shorter sound is produced by the sharp closure of the aortic and the pulmonary valves. The tricuspid valve is best heard over the right half of the lower end of the body of the sternum. The mitral valve is best heard over the apex beat (i.e., at the level of the fifth left intercostal space, approximately 3.5 in. [9 cm] from the midline). The pulmonary valve is best heard over the medial end of the second left intercostal space. The aortic valve is best heard over the medial end of the second right intercostal space.
  37. 37. FAILURE OF THE CONDUCTING SYSTEM OF THE HEART The atrioventricular bundle is the only route by which the cardiac impulse can spread from the atria to the ventricles. Failure of the bundle to conduct the normal impulses results in alteration in the rhythmic contraction of the ventricles or, if complete bundle block occurs, complete dissociation between the atria and the ventricular rates of contraction.
  38. 38. CORONARY ARTERY DISEASE Although the coronary arteries have numerous anastomoses at the arteriolar level, they are essentially functional end arteries. A sudden block of one of the large branches of either coronary artery will usually lead to necrosis of the cardiac muscle in the vasculararea, and often the patient dies
  39. 39. CARDIAC PAIN Pain originating in the heart as the result of ischemia results in the stimulation of the sensory nerve endings in the myocardium. The afferent nerve fibers ascend to the central nervous system via the sympathetic trunk and enter the spinal cord through the upper four thoracic nerves. The pain varies considerably, from a severe crushing pain to nothing more than a mild discomfort. The pain is not felt in the heart but is referred to the skin areas supplied by the corresponding spinal nerves. The skin areas supplied by the upper four intercostal nerves and by the intercostobrachial nerve (T2) are therefore mainly affected.
  40. 40. Atrial Septal Defect In 25% of individuals, the foramen ovale does not completely close. When the opening is small, it has no clinical significance. Occasionally, however, the opening is large, and this results in oxygenated blood from the left atrium passing into the right atrium
  41. 41. Ventricular Septal Defects The ventricular septum is normally formed by fusion of the small, membranous upper part with the larger,lower muscular part. Ventricular septal defects occur in the membranous part of the septum. Oxygenated blood passes through the defect from left to right, causing enlargement of the right ventricle.
  42. 42. Tetralogy of Fallot The following four defects occur with tetralogy of Fallot • Large ventricular septal defeat. • Stenosis of the pulmonary trunk. • Exit of the aorta from the heart immediately above the ventricular septal defect. • Hypertrophy of the right ventricle (because of the resulting high blood pressure in that ventricle).
  43. 43. Patent Ductus Arteriosus Normally, the ductus arteriosus has closed by the end of the first month after birth. Failure of the ductus arteriosus to close results in aortic blood passing into the pulmonary artery, which then raises the pressure in the pulmonary circulation and causes hypertrophy of the right ventricle
  44. 44. Coarctation of the Aorta Coarctation of the aorta is a narrowing of the aorta just proximal, opposite, or distal to the site of Attachment of the ligamentum arteriosum. It arises after birth and is thought to result from the Contraction of ductus arteriosus muscle tissue that Has been incorporated in the wall of the aorta. When The ductus arteriosus contracts normally, the aortic Wall also contracts, and the aortic lumen narrows. Later fibrosis causes permanent narrowing.
  45. 45. AZYGOS VEINS AND CAVAL OBSTRUCTION In obstruction of the superior or inferior venae cavae, the azygos veins provide an alternative pathway for the return of venous blood to the right atrium of the heart.
  46. 46. LOWER THIRD OF ESOPHAGUS AS SITE OF PORTOSYSTEMIC ANASTOMOSIS At the lower third of the esophagus, the tributaries of the azygos veins (systemic circulation) anastomose with the left gastric vein, a tributary of the portal vein. Should the portal vein become obstructed, the veins at the site of the portosystemic anastomosis become dilated and varicosed as the result of the increased flow of blood. This pathologic change is an attempt to return the portal blood to the systemic circulation without going through the normal obstructed channel through the liver.
  47. 47. Surface Anatomy of Thoracic Wall Several bony landmarks and imaginary lines facilitate anatomical descriptions, identification of thoracic areas, and location of lesions such as a bullet wound: • Anterior median (midsternal) line indicates the intersection of the median plane with the Anterior thoracic wall. Midclavicular lines pass through the midpoints of the clavicles, Parallel to the anterior median line . • Anterior axillary line runs vertically along the anterior axillary fold, which is formed by the border of the pectoralis major as it spans from the thorax to the humerus (arm bone). • Midaxillary line runs from the apex (deepest part) of the axilla, parallel to the anterior Axillary line. • Posterior axillary line, also parallel to the anterior axillary line, is drawn vertically along the posterior axillary fold formed by the latissimus dorsi and teres major muscles as they span from the back to the humerus. • Posterior median (midvertebral) line is a vertical line at the intersection of the median plane With the vertebral column. • Scapular lines are parallel to the posterior median line and cross the inferior angles of the scapulae
  48. 48. Additional lines (not illustrated) are extrapolated along borders of bony formations—for example, the parasternal line (G. para, adjacent to). The clavicles lie subcutaneously, forming bony ridges at the junction of the thorax and neck. They can be palpated easily throughout their length, especially where their medial ends articulate with the manubrium. The sternum also lies subcutaneously in the anterior median line and is palpable throughout its length. The manubrium of the sternum: Lies at the level of the bodies of T3 and T4 vertebrae is anterior to the arch of the aorta Has a jugular notch that can be palpated between the prominent sternal ends of the clavicles It has a sternal angle where it articulates with the sternal body at the level of the T4 -T5 IV disc and the space between the third and fourth spinous processes Surface Anatomy of Thoracic Wall
  49. 49. Surface Anatomy of Thoracic Wall The sternal angle is a palpable landmark that lies at the level of the second pair of costal cartilages. The main bronchi pass inferolaterally from the bifurcation of the trachea at the level of the sternal angle. The sternal angle also demarcates the division between the superior and inferior mediastina and the beginning of the arch of the aorta. The superior vena cava passes inferiorly deep to the manubrium, projecting as much as a fingerbreadth to the right of this bone. The first rib cannot be palpated because it lies deep to the clavicle; thus count the ribs and intercostal spaces anteriorly by sliding the fingers laterally from the sternal angle onto the second costal cartilage. Start counting with rib 2 and count the ribs and spaces by moving the fingers inferolaterally. The first intercostal space is inferior to the first rib; likewise, the other spaces lie inferior to the similarly numbered ribs. The body of the sternum lies anterior to the right border of the heart and vertebrae T5-T9. The xiphoid process lies in a slight depression ( the epigast ric fossa) where the converging costal margins form the infrasternal angle. The costal margins, formed by the medial borders of the seventh through tenth costal cartilages, are easily palpable where they extend inferolaterally from the xiphisternal joint . This articulation, often seen as a ridge, is at the level of the inferior border of the T9 vertebra.
  50. 50. Pulmonary Collapse If a sufficient amount of air enters the pleural cavity, the surface tension adhering visceral to parietal pleura (lung to thoracic wall) is broken, and the lung collapses because of its inherent elasticity (elastic recoil). When a lung collapses, the pleural cavity— normally a potential space, purple)—becomes a real space. The pleural cavity is located between the parietal pleura (blue) and the visceral pleura (red). One lung may be collapsed after surgery, for example, without collapsing the other because the pleural sacs are separate.
  51. 51. Pneumothorax, Hydrothorax, Hemothorax, and Chylothorax Entry of air into the pleural cavity—pneumothorax —resulting from a penetrating wound of the parietal pleura or rupture of a lung from a bullet, for example, results in partial collapse of the lung. Fractured ribs may also tear the parietal pleura and produce pneumothorax. This may also occur as a result of leakage from the lung through an opening in the visceral pleura. The accumulation of a significant amount of fluid in the pleural cavity —hydrothorax—may result from pleural effusion (escape of fluid into the pleural cavity). With a chest wound, blood may also enter the pleural cavity (hemothorax); this condition results more often from injury to a major intercostal vessel than from laceration of a lung. Lymph from a torn thoracic duct may also enter the pleural cavity (chylothorax). Chyle is a pale white or yellow lymph fluid in the thoracic duct containing fat absorbed by the intestines
  52. 52. Pleuritis During inspiration and expiration, the normally moist, smooth pleurae make no sound detectable by auscultation (listening to breath sounds); however, inflammation of the pleurae—pleuritis (pleurisy)— makes the lung surfaces rough. The resulting friction (pleural rub) may be heard with a stethoscope. Acute pleuritis is marked by sharp, stabbing pain, especially on exertion, such as climbing stairs, when the rate and depth of respiration may be increased even slightly.
  53. 53. Variation in Lobes of Lungs • Occasionally, an extra fissure divides a lung or a fissure is absent. For example, the left lung sometimes has three lobes and the right lung only two. The most common “accessory” lobe is the azygos lobe, which appears in the right lung in approximately 1% of people. In these cases, the azygos vein arches over the apex of the right lung and not over the right hilum, isolating the medial part of the apex as an azygos lobe.
  54. 54. Thoracentesis • Sometimes it is necessary to insert a hypodermic needle through an intercostal space into the pleural cavity to obtain a sample of pleural fluid or to remove blood or pus. To avoid damage to the intercostal nerve and vessels, the needle is inserted superior to the rib, high enough to avoid the collateral branches.a
  55. 55. Auscultation and Percussion of Lungs Auscultation of the lungs (assessing air flow through the tracheobronchial tree into the lung with a stethoscope) and percussion of the lungs (tapping the chest over the lungs with the finger) always includes the root of the neck to detect sounds in the apices of the lungs. Percussion helps establish whether the underlying tissues are air- filled (resonant sound), fluid-filled (dull sound), or solid (flat sound). When physicians refer to the base of a lung, they are usually not referring to its diaphragmatic surface (base); rather, they are referring to the inferior part of the posterior costal surface of the inferior lobe. To auscultate this area, physicians apply a stethoscope to the inferoposterior aspect of the thoracic wall at the level of the T10 vertebra.
  56. 56. Aspiration of Foreign Bodies Because the right bronchus is wider and shorter and runs more vertically than the left ronchus, aspirated foreign bodies are more likely to enter and lodge in it or one of its branches. A potential hazard encountered by dentists is an aspirated foreign body, such as a piece of tooth or filling material. Such objects are also most likely to enter the right main bronchus.
  57. 57. Lung Resections Knowledge of the anatomy of the bronchopulmonary segments is essential for precise interpretations of diagnostic images of the lungs and for surgical resection (removal) of diseased segments. When resecting a bronchopulmonary segment, surgeons follow the interlobar veins to pass between the segments. Bronchial and pulmonary disorders such as tumors or abscesses (collections of pus) often localize in a bronchopulmonary segment, which may be surgically resected. During the treatment of lung cancer, the surgeon may remove a whole lung (pneumonectomy), a lobe (lobectomy), or one or more bronchopulmonary segments (segmentectomy). Knowledge and understanding of the bronchopulmonary segments and their relationship to the bronchial tree are also essential for planning drainage and clearance techniques used in physical therapy for enhancing drainage from specific areas (e.g., in patients with pneumonia or cystic fibrosis).
  58. 58. Injury to Pleurae The visceral pleura is insensitive to pain because its innervation is autonomic (motor and visceral afferent). The autonomic nerves reach the visceral pleura in company with the bronchial vessels. The visceral pleura receives no nerves of general sensation. In contrast, the parietal pleura is sensitive to pain, particularly the costal pleura, because it is richly supplied by branches of the somatic intercostal and phrenic nerves. Irritation of the parietal pleura produces local pain and referred pain to the areas sharing innervation by the same segments of the spinal cord. Irritation of the costal and peripheral parts of the diaphragmatic pleura results in local pain and referred pain along the intercostal nerves to the thoracic and abdominal walls. Irritation of the mediastinal and central diaphragmatic areas of the parietal pleura results in pain that is referred to the root of the neck and over the shoulder (C3-C5 dermatomes).
  59. 59. Thoracoscopy Thoracoscopy is a diagnostic and sometimes therapeutic procedure in which the pleural cavity is examined with a thoracoscope. Small incisions are made into the pleural cavity via an intercostal space. In addition to observation, biopsies can be taken and some thoracic conditions can be treated (e.g., disrupting adhesions or removing plaques).
  60. 60. Pulmonary Embolism Obstruction of a pulmonary artery by a blood clot (embolus) is a common cause of morbidity (sickness) and mortality (death). An embolus in a pulmonary artery forms when a blood clot, fat globule, or air bubble travels in the blood to the lungs from a leg vein. The embolus passes through the right side of the heart to a lung through a pulmonary artery. The embolus may block a pulmonary artery— pulmonary embolism—or one of its branches. The immediate result is partial or complete obstruction of blood flow to the lung. The obstruction results in a sector of lung that is ventilated but not perfused with blood. When a large embolus occludes a pulmonary artery, the person suffers acute respiratory distress because of a major decrease in the oxygenation of blood owing to blockage of blood flow through the lung. A medium-size embolus may block an artery supplying a bronchopulmonary segment, producing a pulmonary infarct, an area of necrotic (dead) lung tissue.
  61. 61. Inhalation of Carbon Particles • Lymph from the lungs carries phagocytes, cells possessing the property of ingesting carbon particles from inspired air. In many people, especially cigarette smokers, these particles color the surface of the lungs and associated lymph nodes a mottled gray to black. Smokers' cough results from inhalation of irritants in tobacco.
  62. 62. Bronchogenic Carcinoma Bronchogenic carcinoma is a common type of lung cancer that arises from the epithelium of the bronchial tree. Lung cancer is mainly caused by cigarette smoking. Bronchogenic carcinoma usually metastasizes widely because of the arrangement of the lymphatics. The tumor cells probably enter the systemic circulation by invading the wall of a sinusoid or venule in the lung and are transported through the pulmonary veins, left heart, and aorta to all parts of the body, especially the cranium and brain.
  63. 63. Bronchoscopy When examining the bronchi with a bronchoscope — an endoscope for inspecting the interior of the tracheobronchial tree for diagnostic purposes—one can observe a ridge, the carina, between the orifices of the main bronchi . The carina is a cartilaginous projection of the last tracheal ring. If the tracheobronchial lymph nodes in the angle between the main bronchi are enlarged because cancer cells have metastasized from a bronchogenic carcinoma, for example, the carina is distorted, widened posteriorly, and immobile.
  64. 64. Surgical Significance of Transverse Pericardial Sinus The transverse pericardial sinus is especially important to cardiac surgeons. After the pericardial sac has been opened anteriorly, a finger can be passed through the transverse pericardial sinus posterior to the aorta and pulmonary trunk. By passing a surgical clamp or placing a ligature around these vessels, inserting the tubes of a coronary bypass machine, and then tightening the ligature, surgeons can stop or divert the circulation of blood in these large arteries while performing cardiac surgery, such as coronary artery bypass grafting. Cardiac surgery is performed while the patient is on cardiopulmonary bypass.
  65. 65. Pericarditis and Pericardial Effusion Inflammation of the pericardium (pericarditis) usually causes chest pain. Normally, the layers of serous pericardium make no detectable sound during auscultation. However, pericarditis makes the surfaces rough and the resulting friction, pericardial friction rub, sounds like the rustle of silk when listening with a stethoscope. Certain inflammatory diseases may also produce pericardial effusion (passage of fluid from the pericardial capillaries into the pericardial cavity). As a result, the heart becomes compressed (unable to expand and fill fully) and ineffectual.
  66. 66. Cardiac Tamponade Cardiac tamponade (heart compression) is a potentially lethal condition because the fibrous pericardium is tough and inelastic. Consequently, heart volume is increasingly compromised by the fluid outside the heart but inside the pericardial cavity. When there is a slow increase in the size of the heart, cardiomegaly, the pericardium allows the enlargement of the heart to occur without compression. Stab wounds that pierce the heart, causing blood to enter the pericardial cavity (hemopericardium), also risk producing cardiac tamponade. Hemopericardium may also result from perforation of a weakened area of heart muscle after a heart attack. As blood accumulates, the heart is compressed and circulation fails. Pericardiocentesis (drainage of serous fluid from pericardial cavity) is usually necessary to relieve the cardiac tamponade. To remove the excess fluid, a wide-bore needle may be inserted through the left fifth or sixth intercostal space near the sternum.
  67. 67. Levels of Viscera in Mediastinum The level of the viscera relative to the mediastinal subdivisions depends on the position of the person. When a person is lying supine, the level of the viscera relative to the subdivisions of the mediastinum is as shown in the figures in this text. Anatomical descriptions traditionally describe the level of the viscera as if the person were supine. However, in the standing position, the levels of the viscera are as shown in Figure B1.12. This occurs because the soft structures in the mediastinum, the heart and great vessels, and the abdominal viscera supporting them sag inferiorly under the influence of gravity. This movement of mediastinal structures must be considered during physical and radiological examinations.
  68. 68. Percussion of Heart Percussion defines the density and size of the heart. The classic percussion technique is to create vibration by tapping the chest with a finger while listening and feeling for differences in sound wave conduction. Percussion is performed at the third, fourth, and fifth intercostal spaces from the left anterior axillary line to the right anterior axillary line. Normally the percussion note changes from resonance to dullness (because of the presence of the heart) approximately 6 cm lateral to the left border of the sternum. The character of the sound changes as different areas of the chest are tapped.
  69. 69. Atrial and Ventricular Septal Defects Congenital anomalies of the interatrial septum —usually related to incomplete closure of the oval foramen—are atrial septal defects or ASDs. A probe-size patency (defect) appears in the superior part of the oval fossa in 15% to 25% of people. These small ASDs, by themselves, are usually of no clinical significance; however, large ASDs allow oxygenated blood from the lungs to be shunted from the left atrium through the defect into the right atrium, causing enlargement of the right atrium and ventricle and dilation of the pulmonary trunk. The membranous part of the IV septum develops separately from the muscular part and has a complex embryological origin. Consequently, this part is the common site of ventricular septal defects or VSDs . These congenital anomalies rank first on all lists of cardiac defects. Isolated VSDs account for approximately 25% of all forms of congenital heart disease (Moore & Persaud, 2008). The size of the defect varies from 1 to 25 mm. A VSD causes a left-toright shunt of blood through the defect. A large shunt increases pulmonary blood flow, which causes pulmonary disease (hypertension, or increased blood pressure) and may cause cardiac failure.
  70. 70. Thrombi Thrombi (clots) form on the walls of the left atrium in certain types of heart disease. If these thrombi detach or if pieces break off, they pass into the systemic circulation and occlude peripheral arteries. Occlusion of an artery in the brain results in a stroke or cerebrovascular accident (CVA), which may affect, for example, vision, cognition, or sensory or motor function of parts of the body previously controlled by the now-damaged area of the brain.
  71. 71. Valvular Heart Disease Disorders involving the valves of the heart disturb the pumping efficiency of the heart. Valvular heart disease produces either stenosis (narrowing) or insufficiency. Stenosis is the failure of a valve to open fully, slowing blood flow from a chamber. Valvular insufficiency or regurgitat ion, on the other hand, is failure of the valve to close completely, usually owing to nodule formation on (or scarring and contraction of) the cusps so that the edges do not meet or align. This allows a variable amount of blood (depending on the severity) to flow back into the chamber it was just ejected from. Both stenosis and insufficiency result in an increased orkload for the heart. Restriction of high-pressure blood flow (stenosis) and passage of blood through a narrow opening into a larger vessel or chamber (stenosis and regurgitation) produce turbulence. Turbulence sets up eddies (small whirlpools) that produce vibrations that are audible as murmurs. Superficial vibratory sensations—thrills—may be felt on the skin over an area of turbulence.
  72. 72. valvuloplasty Because valvular diseases are mechanical problems, damaged or defective cardiac valves are often replaced surgically in a procedure called valvuloplasty. Most commonly, artificial valve prostheses made of synthetic materials are used in these valve replacement procedures, but xenografted valves (valves transplanted from other species, such as pigs) are also used.
  73. 73. Valve stenosis A prolapsed mitral valve is an insufficient or incompetent valve in which one or both leaflets are enlarged, redundant or “floppy,” and extending back into the left atrium during systole. As a result, blood regurgitates into the left atrium when the left ventricle contracts, producing a characteristic murmur. Aortic valve stenosis is the most frequent valve abnormality and results in left ventricular hypertrophy. The great majority of cases of aortic stenosis result from degenerative calcification. In pulmonary valve stenosis (narrowing), the valve cusps are fused, forming a dome with a narrow central opening. In infundibular pulmonary stenosis, the conus arteriosus is underdeveloped, producing a restriction of right ventricular outflow. The degree of hypertrophy of the right ventricle is variable.
  74. 74. Coronary Artery Disease or Coronary Heart Disease Coronary artery disease (CAD) is one of the leading causes of death. It has many causes, all of which result in a reduced blood supply to the vital myocardial tissue.
  75. 75. Myocardial Infarction With sudden occlusion of a major artery by an embolus (G. embolos, plug), the region of myocardium supplied by the occluded vessel becomes infarcted (rendered virtually bloodless) and undergoes necrosis (pathological tissue death). The three most common sites of coronary artery occlusion are (1) the anterior IV (LAD) branch of the LCA (40-50%), (2) the RCA (30- 40%), and (3) the circumflex branch of the LCA (15- 20%). An area of myocardium that has undergone necrosis constitutes a myocardial infarct ion (MI). The most common cause of ischemic heart disease is coronary artery insufficiency resulting from atherosclerosis.
  76. 76. Coronary Atherosclerosis The atherosclerot ic process, characterized by lipid deposits in the intima (lining layer) of the coronary arteries, begins during early adulthood and slowly results in stenosis of the lumina of the arteries. Insufficiency of blood supply to the heart (myocardial ischemia) may result in MI.
  77. 77. Coronary Bypass Graft Patients with obstruction of their coronary circulation and severe angina may undergo a coronary bypass graft operation. A segment of an artery or vein is connected to the ascending aorta or to the proximal part of a coronary artery and then to the coronary artery distal to the stenosis . The great saphenous vein is commonly harvested for coronary bypass surgery because it (1) has a diameter equal to or greater than that of the coronary arteries, (2) can be easily dissected from the lower limb, (3) and offers relatively lengthy portions with a minimum occurrence of valves or branching. Reversal of the implanted segment of vein can negate the effect of a valve if a valved segment must be used. Use of the radial artery in bypass surgery has become increasingly more common. A coronary bypass graft shunts blood from the aorta to a stenotic coronary artery to increase the flow distal to the obstruction. Revascularization of the myocardium may also be achieved by surgically anastomosing an internal thoracic artery with a coronary artery.
  78. 78. Coronary Angioplasty In selected patients, surgeons use percutaneous transluminal coronary angioplasty, in which they pass a catheter with a small inflatable balloon attached to its tip into the obstructed coronary artery. When the catheter reaches the obstruction, the balloon is inflated, flattening the atherosclerotic plaque against the vessel's wall, and the vessel is stretched to increase the size of the lumen, thus improving blood flow. In other cases, thrombokinase is injected through the catheter; this enzyme dissolves the blood clot. After dilation of the vessel, an intravascular stent may be introduced to maintain the dilation.
  79. 79. Variations of Coronary Arteries Variations in the branching patterns of the coronary arteries are common. In the most common right-dominant pattern, the RCA and LCA share approximately equally in the blood supply to the heart. In approximately 15% of hearts, the LCA is dominant in that the posterior IV branch is a branch of the circumflex artery. There is codominance in about 18% of people, in which branches of both the RCA and LCA reach the crux and give rise to branches that course in or near the posterior IV groove. A few people have only a single coronary artery. In other people, the circumflex artery arises from the right aortic sinus. The branches of coronary arteries are considered to be end arteries—ones that supply regions of the myocardium without functional overlap from other large branches. However, anastomoses exist between small branches of the coronary arteries. The potential for development of collateral circulation likely exists in most hearts.
  80. 80. Echocardiography Echocardiography (ultrasonic cardiography) is a method of graphically recording the position and motion of the heart by the echo obtained from beams of ultrasonic waves directed through the thorax. This technique may detect as little as 20 mL of fluid in the pericardial cavity, such as that resulting from pericardial effusion. Doppler echocardiography is a technique that demonstrates and records the flow of blood through the heart and great vessels by Doppler ultrasonography, making it especially useful In the diagnosis and analysis of problems with blood flow through the heart, such as septal defects, and in delineating valvular stenosis and regurgitation, especially on the left side of the heart.
  81. 81. Cardiac Referred Pain The heart is insensitive to touch, cutting, cold, and heat; however, ischemia and the accumulation of metabolic products stimulate pain endings in the myocardium. The afferent pain fibers run centrally in the middle and inferior cervical branches and especially in the thoracic cardiac branches of the sympathetic trunk. The axons of these primary sensory neurons enter spinal cord segments T1-T4 or T5, especially on the left side. Cardiac referred pain is a phenomenon whereby noxious stimuli originating in the heart are perceived by the person as pain arising from a superficial part of the body—the skin on the medial aspect of the left upper limb, for example. Visceral pain is transmitted by visceral afferent fibers accompanying sympathetic fibers and is typically referred to somatic structures or areas such as the upper limb having afferent fibers with cell bodies in the same spinal ganglion, and central processes that enter the spinal cord through the same posterior roots.
  82. 82. Injury to Conducting System of Heart Damage to the conducting system, often resulting from ischemia caused by coronary artery disease, produces disturbances of cardiac muscle contraction. Because the anterior IV branch (LAD branch) supplies the AV bundle in most people and because branches of the RCA supply both the SA and the AV nodes, parts of the conducting system of the heart are likely to be affected by their occlusion. Damage to the AV node or bundle results in a heart block because the atrial excitation does not reach the ventricles. As a result, the ventricles begin to contract independently at their own rate (25 to 30 times per minute), which is slower than the lowest normal rate of 40 to 45 times per minute. Damage to one of the bundle branches results in a bundle branch block, in which excitation passes along the unaffected branch and causes a normally timed systole of that ventricle only. The impulse then spreads to the other ventricle, producing a late asynchronous contraction.
  83. 83. Laceration of Thoracic Duct • Because the thoracic duct is thin-walled and may be colorless, it may not be easily identified. Consequently, it is vulnerable to inadvertent injury during investigative and/or surgical procedures in the posterior mediastinum. • Laceration of the thoracic duct results in chyle escaping into the thoracic cavity. Chyle may also enter the pleural cavity, producing chylothorax
  84. 84. Collateral Venous Routes to Heart The azygos, hemiazygos, and accessory hemiazygos veins offer alternate means of venous drainage from the thoracic, abdominal, and back regions when obstruction of the IVC occurs. In some people, an accessory azygos vein parallels the main azygos vein on the right side. Other people have no hemiazygos system of veins. A clinically important variation, although uncommon, is when the azygos system receives all the blood from the IVC, except that from the liver. In these people, the azygos system drains nearly all the blood inferior to the diaphragm, except from the digestive tract. When obstruction of the SVC occurs superior to the entrance of the azygos vein, blood can drain inferiorly into the veins of the abdominal wall and return to the right atrium through the IVC and azygos system of veins.
  85. 85. Aneurysm of Ascending Aorta The distal part of the ascending aorta receives a strong thrust of blood when the left ventricle contracts. Because its wall is not yet reinforced by fibrous pericardium (the fibrous pericardium blends with the aortic adventitia at the beginning of the arch), an aneurysm (localized dilation) may develop. An aortic aneurysm is evident on a chest film (radiograph of the thorax) or a magnetic resonance angiogram as an enlarged area of the ascending aorta silhouette. Individuals with an aneurysm usually complain of chest pain that radiates to the back. The aneurysm may exert pressure on the trachea, esophagus, and recurrent laryngeal nerve, causing difficulty in breathing and swallowing.
  86. 86. Injury to Recurrent Laryngeal Nerves The recurrent laryngeal nerves supply all the intrinsic muscles of the larynx, except one. Consequently, any investigative procedure or disease process in the superior mediastinum may involve these nerves and affect the voice. Because the left recurrent laryngeal nerve hooks around the arch of the aorta and ascends between the trachea and the esophagus, it may be involved when there is a bronchial or esophageal carcinoma, enlargement of mediastinal lymph nodes, or an aneurysm of the arch of the aorta. In the latter condition, the nerve may be stretched by the dilated arch of the aorta.
  87. 87. Variat ions of Great Arteries The most superior part of the arch of the aorta is usually approximately 2.5 cm inferior to the superior border of the manubrium, but it may be more superior or inferior. Sometimes the arch curves over the root of the right lung and passes inferiorly on the right side, forming a right arch of the aorta. Less frequently, a double arch of the aorta or ret roesophageal right subclavian artery form a vascular ring around the esophagus and trachea. If the trachea is compressed enough to affect breathing, surgical division of the vascular ring may be needed. Variations in the origin of the branches of the arch are fairly common. The usual pattern of branches of the arch of the aorta is present in approximately 65% of people. In approximately 27% of people, the left common carotid artery originates from the brachiocephalic trunk. A brachiocephalic trunk fails to form in approximately 2.5% of people; in these cases each of the four arteries (right and left common carotid and subclavian arteries) originate independently from the arch of the aorta (Bergman et al., 1988)
  88. 88. Coarctation of Aorta • In coarctat ion of the aorta, the arch of the aorta or descending aorta has an abnormal narrowing (stenosis) that diminishes the caliber of the aortic lumen, producing an obstruction to blood flow to the inferior part of the body. The most common site for a coarctation is near the ligamentum arteriosum. When the coarctation is inferior to this site (postductal coarctation), a good collateral circulation usually develops between the proximal and distal parts of the aorta through the intercostal and internal thoracic arteries.
  89. 89. Age Changes in Thymus The thymus is a prominent feature of the superior mediastinum during infancy and childhood. In some infants, the thymus may compress the trachea. The thymus plays an important role in the development and maintenance of the immune system. As puberty is reached, the thymus begins to diminish in relative size. By adulthood, it is usually replaced by adipose tissue and is often scarcely recognizable; however, it continues to produce T lymphocytes.
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